In physics, time and space are closely related.

He received the letter challenging him to a duel and began preparing for the duel.

His role is to fulfill his responsibilities as a leader.

Gender roles are an important element in defining individual behavior in society.

It is important to understand the importance of health.

He is a world-famous mathematician.

Combinatorics is a branch of mathematics that studies combinations of things.

Combinatorics is a branch of mathematics dealing with issues of order and choice.

Combinatorics is a branch of mathematics that studies combinations of things.

Discrete mathematics is an important field that forms the basis of computer science.